A very-low carbohydrate content in a high-fat diet modifies the plasma metabolome and impacts systemic inflammation and experimental atherosclerosis

Ketogenic diets (KDs) are very high-fat low-carbohydrate diets that promote nutritional ketosis and are widely used for weight loss, although concerns about potential adverse cardiovascular effects remain. We investigated a very high-fat KD's vascular impact and plasma metabolic signature compared to a non-ketogenic high-fat diet (HFD). Apolipoprotein E deficient (ApoE -/-) mice were fed a KD (%kcal:81:1:18, fat/carbohydrate/protein), a non-ketogenic high-fat diet with half of the fat content (HFD) (%kcal:40:42:18, fat/carbohydrate/protein) for 12 weeks. Plasma samples were used to quantify the major ketone body beta-hydroxybutyrate (BHB) and several pro-inflammatory cytokines (IL-6, MCP-1, MIP-1alpha, and TNF alpha), and to targeted metabolomic profiling by mass spectrometry. In addition, aortic atherosclerotic lesions were quantified ex-vivo by magnetic resonance imaging (MRI) on a 14-tesla system. KD was atherogenic when compared to the control diet, but KD mice, when compared to the HFD group (1) had markedly higher levels of BHB and lower levels of cytokines, confirming the presence of ketosis that alleviated the well-established fat-induced systemic inflammation; (2) displayed significant changes in the plasma metabolome that included a decrease in lipophilic metabolites and an increase in hydrophilic metabolites; (3) had significantly lower levels of several atherogenic lipid metabolites, including phosphatidylcholines, cholesterol esters, sphingomyelins, and ceramides; and (4) presented significantly lower aortic plaque burden. KD was atherogenic and was associated with specific metabolic changes but alleviated the fat-induced inflammation and lessened the progression of atherosclerosis when compared to the HFD.

VCAM-1-targeted nanoparticles to diagnose, monitor and treat atherosclerosis

Vascular cell adhesion molecule-1 (VCAM-1) was identified over 2 decades ago as an endothelial adhesion receptor involved in leukocyte recruitment and cell-based immune responses. In atherosclerosis, a chronic inflammatory disease of the blood vessels that is the leading cause of death in the USA, endothelial VCAM-1 is robustly expressed beginning in the early stages of the disease. The interactions of circulating immune cells with VCAM-1 on the activated endothelial cell surface promote the uptake of monocytes and the progression of atherosclerotic lesions in susceptible vessels. Herein, we review the role of VCAM-1 in atherosclerosis and the use of VCAM-1 binding peptides, antibodies and aptamers as targeting agents for nanoplatforms for early detection and treatment of atherosclerotic disease.

Diet-Induced Severe Hyperhomocysteinemia Promotes Atherosclerosis Progression and Dysregulates the Plasma Metabolome in Apolipoprotein-E-Deficient Mice

Atherosclerosis and resulting cardiovascular disease are the leading causes of death in the US. Hyperhomocysteinemia (HHcy), or the accumulation of the intermediate amino acid homocysteine, is an independent risk factor for atherosclerosis, but the intricate biological processes mediating this effect remain elusive. Several factors regulate homocysteine levels, including the activity of several enzymes and adequate levels of their coenzymes, including pyridoxal phosphate (vitamin B6), folate (vitamin B9), and methylcobalamin (vitamin B12). To better understand the biological influence of HHcy on the development and progression of atherosclerosis, apolipoprotein-E-deficient (apoE-/- mice), a model for human atherosclerosis, were fed a hyperhomocysteinemic diet (low in methyl donors and B vitamins) (HHD) or a control diet (CD). After eight weeks, the plasma, aorta, and liver were collected to quantify methylation metabolites, while plasma was also used for a broad targeted metabolomic analysis. Aortic plaque burden in the brachiocephalic artery (BCA) was quantified via 14T magnetic resonance imaging (MRI). A severe accumulation of plasma and hepatic homocysteine and an increased BCA plaque burden were observed, thus confirming the atherogenic effect of the HHD. Moreover, a decreased methylation capacity in the plasma and aorta, indirectly assessed by the ratio of S-adenosylmethionine to S-adenosylhomocysteine (SAM:SAH) was detected in HHD mice together with a 172-fold increase in aortic cystathionine levels, indicating increased flux through the transsulfuration pathway. Betaine and its metabolic precursor, choline, were significantly decreased in the livers of HHD mice versus CD mice. Widespread changes in the plasma metabolome of HHD mice versus CD animals were detected, including alterations in acylcarnitines, amino acids, bile acids, ceramides, sphingomyelins, triacylglycerol levels, and several indicators of dysfunctional lipid metabolism. This study confirms the relevance of severe HHcy in the progression of vascular plaque and suggests novel metabolic pathways implicated in the pathophysiology of atherosclerosis.

High-field magnetic resonance microscopy of aortic plaques in a mouse model of atherosclerosis

OBJECTIVES

Pre-clinical models of human atherosclerosis are extensively used; however, traditional histological methods do not allow for a holistic view of vascular lesions. We describe an ex-vivo, high-resolution MRI method that allows the 3 dimensional imaging of the vessel for aortic plaque visualization and quantification.

MATERIALS AND METHODS

Aortas from apolipoprotein-E-deficient (apoE-/-) mice fed an atherogenic diet (group 1) or a control diet (group 2) were subjected to 14 T MR imaging using a 3D gradient echo sequence. The obtained data sets were reconstructed (Matlab), segmented, and analyzed (Avizo). The aortas were further sectioned and subjected to traditional histological analysis (Oil-Red O and hematoxylin staining) for comparison.

RESULTS

A resolution up to 15 × 10x10 μm3 revealed that plaque burden (mm3) was significantly (p < 0.05) higher in group 1 (0.41 ± 0.25, n = 4) than in group 2 (0.01 ± 0.01, n = 3). The achieved resolution provided similar detail on the plaque and the vessel wall morphology compared with histology. Digital image segmentation of the aorta's lumen, plaque, and wall offered three-dimensional visualizations of the entire, intact aortas.

DISCUSSION

14 T MR microscopy provided histology-like details of pathologically relevant vascular lesions. This work may provide the path research needs to take to enable plaque characterization in clinical applications.

Selective head cooling in the acute phase of concussive injury: a neuroimaging study

Introduction

Neurovascular decoupling is a common consequence after brain injuries like sports-related concussion. Failure to appropriately match cerebral blood flow (CBF) with increases in metabolic demands of the brain can lead to alterations in neurological function and symptom presentation. Therapeutic hypothermia has been used in medicine for neuroprotection and has been shown to improve outcome. This study aimed to examine the real time effect of selective head cooling on healthy controls and concussed athletes via magnetic resonance spectroscopy (MRS) and arterial spin labeling (ASL) measures.

Methods

24 participants (12 controls; 12 concussed) underwent study procedures including the Post-Concussion Symptom Severity (PCSS) Rating Form and an MRI cooling protocol (pre-cooling (T1 MPRAGE, ASL, single volume spectroscopy (SVS)); during cooling (ASL, SVS)).

Results

Results showed general decreases in brain temperature as a function of time for both groups. Repeated measures ANOVA showed a significant main effect of time (F = 7.94, p < 0.001) and group (F = 22.21, p < 0.001) on temperature, but no significant interaction of group and time (F = 1.36, p = 0.237). CBF assessed via ASL was non-significantly lower in concussed individuals at pre-cooling and generalized linear mixed model analyses demonstrated a significant main effect of time for the occipital left ROI (F = 11.29, p = 0.002) and occipital right ROI (F = 13.39, p = 0.001). There was no relationship between any MRI metric and PCSS symptom burden.

Discussion

These findings suggest the feasibility of MRS thermometry to monitor alterations of brain temperature in concussed athletes and that metabolic responses in response to cooling after concussion may differ from controls.

High-frequency neuronal signal better explains multi-phase BOLD response

Visual stimulation-evoked blood-oxygen-level dependent (BOLD) responses can exhibit more complex temporal dynamics than a simple monophasic response. For instance, BOLD responses sometimes include a phase of positive response followed by a phase of post-stimulus undershoot. Whether the BOLD response during these phases reflects the underlying neuronal signal fluctuations or is contributed by non-neuronal physiological factors remains elusive. When presenting blocks of sustained (i.e. DC) light ON-OFF stimulations to unanesthetized rats, we observed that the response following a decrease in illumination (i.e. OFF stimulation-evoked BOLD response) in the visual cortices displayed reproducible multiple phases, including an initial positive BOLD response, followed by an undershoot and then an overshoot before the next ON trial. This multi-phase BOLD response did not result from the entrainment of the periodic stimulation structure. When we measured the neural correlates of these responses, we found that the high-frequency band from the LFP power (300 - 3000 Hz, multi-unit activity (MUA)), but not the power in the gamma band (30 - 100 Hz) exhibited the same multiphasic dynamics as the BOLD signal. This study suggests that the post-stimulus phases of the BOLD response can be better explained by the high-frequency neuronal signal.

Nutritional Ketosis, Aquaporins, and Energy Homeostasis

Objectives

Ketogenic diets (KDs), promoting nutritional ketosis, profoundly impact energetic metabolism, and are being widely used for weight loss purposes. Aquaporins (AQPs) are transmembrane channels that facilitate water and glycerol transport across cell membranes and are critical players in energy homeostasis. The axis of adipose AQP7/hepatic AQP9 assures the body's glycerol homeostasis. Studies investigating the relation between KD, aquaporins, and energy homeostasis are scarce.

Methods

ApoE−/− mice were fed ad libitum a KD (Kcal%: 1/81/18, carbohydrate/fat/protein; n = 8) or a control diet (Kcal%: 70/11/18, carbohydrate/fat/protein; n = 7) for 12 weeks. Food consumption and body weight were determined weekly, and plasma was collected every 4 weeks for biochemical analyses. Upon euthanasia, the tissues involved in energy homeostasis, the liver, white adipose tissue (WAT), and brown adipose tissue (BAT), were collected for gene expression analysis.

Results

Bodyweight gain (% to the initial weight) was similar in both groups (4.0 ± 1.1, KD-mice vs. 3.3 ± 1.3, controls), in spite of the profoundly different diet fat content, thus confirming the anti-obesogenic effect of the diet. The plasma concentration of the major ketone body, ß-hydroxybutyrate, was significantly elevated in KD (2,019 ± 87 vs. control, 418 ± 72 nM, mean ± SEM), confirming the presence of nutritional ketosis under this dietary condition. The transcript level for uncoupling protein 1 (Ucp1) gene in BAT of KD-fed mice was upregulated by 400%, compared to control-fed mice, unveiling a thermogenic effect of KD. Lastly, mice subjected to KD exhibited: in BAT, a significant KD-induced upregulation of Aqp9 transcripts suggesting the participation in the influx of excess plasma glycerol to fuel thermogenesis; in WAT, a downregulation of Aqp7, suggesting the non-utilization of adipocyte lipid droplets as fuel; in the liver, an Aqp7 up-regulation suggesting its participation in glycerol influx into hepatocytes.

Conclusions

The anti-obesogenic effect of KD was associated with the upregulation of thermogenic genes in BAT and with the modulation of AQPs expression patterns in BAT, WAT, and the liver

Funding Sources

Magnetic Resonance Imaging Facility, The Huck Institutes of the Life Sciences, Penn State, USA Fundação para a Ciência e Tecnologia (FCT), Portugal.

The Effect of Nutritional Ketosis on Aquaporin Expression in Apolipoprotein E-Deficient Mice: Potential Implications for Energy Homeostasis

Ketogenic diets (KDs) are very low-carbohydrate, very high-fat diets which promote nutritional ketosis and impact energetic metabolism. Aquaporins (AQPs) are transmembrane channels that facilitate water and glycerol transport across cell membranes and are critical players in energy homeostasis. Altered AQP expression or function impacts fat accumulation and related comorbidities, such as the metabolic syndrome. Here, we sought to determine whether nutritional ketosis impacts AQPs expression in the context of an atherogenic model. To do this, we fed ApoE^−/− (apolipoprotein E-deficient) mice, a model of human atherosclerosis, a KD (Kcal%: 1/81/18, carbohydrate/fat/protein) or a control diet (Kcal%: 70/11/18, carbohydrate/fat/protein) for 12 weeks. Plasma was collected for biochemical analysis. Upon euthanasia, livers, white adipose tissue (WAT), and brown adipose tissue (BAT) were used for gene expression studies. Mice fed the KD and control diets exhibited similar body weights, despite the profoundly different fat contents in the two diets. Moreover, KD-fed mice developed nutritional ketosis and showed increased expression of thermogenic genes in BAT. Additionally, these mice presented an increase in Aqp9 transcripts in BAT, but not in WAT, which suggests the participation of Aqp9 in the influx of excess plasma glycerol to fuel thermogenesis, while the up-regulation of Aqp7 in the liver suggests the involvement of this aquaporin in glycerol influx into hepatocytes. The relationship between nutritional ketosis, energy homeostasis, and the AQP network demands further investigation.

Quantitative monitoring of paramagnetic contrast agents and their allocation in plant tissues via DCE-MRI

BACKGROUND

Studying dynamic processes in living organisms with MRI is one of the most promising research areas. The use of paramagnetic compounds as contrast agents (CA), has proven key to such studies, but so far, the lack of appropriate techniques limits the application of CA-technologies in experimental plant biology. The presented proof-of-principle aims to support method and knowledge transfer from medical research to plant science.

RESULTS

In this study, we designed and tested a new approach for plant Dynamic Contrast Enhanced Magnetic Resonance Imaging (pDCE-MRI). The new approach has been applied in situ to a cereal crop (Hordeum vulgare). The pDCE-MRI allows non-invasive investigation of CA allocation within plant tissues. In our experiments, gadolinium-DTPA, the most commonly used contrast agent in medical MRI, was employed. By acquiring dynamic T₁-maps, a new approach visualizes an alteration of a tissue-specific MRI parameter T₁ (longitudinal relaxation time) in response to the CA. Both, the measurement of local CA concentration and the monitoring of translocation in low velocity ranges (cm/h) was possible using this CA-enhanced method.

CONCLUSIONS

A novel pDCE-MRI method is presented for non-invasive investigation of paramagnetic CA allocation in living plants. The temporal resolution of the T₁-mapping has been significantly improved to enable the dynamic in vivo analysis of transport processes at low-velocity ranges, which are common in plants. The newly developed procedure allows to identify vascular regions and to estimate their involvement in CA allocation. Therefore, the presented technique opens a perspective for further development of CA-aided MRI experiments in plant biology.

A Hypomethylating Ketogenic Diet in Apolipoprotein E-Deficient Mice: A Pilot Study on Vascular Effects and Specific Epigenetic Changes

Hyperhomocysteneinemia (HHcy) is common in the general population and is a risk factor for atherosclerosis by mechanisms that are still elusive. A hypomethylated status of epigenetically relevant targets may contribute to the vascular toxicity associated with HHcy. Ketogenic diets (KD) are diets with a severely restricted amount of carbohydrates that are being widely used, mainly for weight-loss purposes. However, studies associating nutritional ketosis and HHcy are lacking. This pilot study investigates the effects of mild HHcy induced by nutritional manipulation of the methionine metabolism in the absence of dietary carbohydrates on disease progression and specific epigenetic changes in the apolipoprotein-E deficient (apoE^-/-) mouse model. ApoE^-/- mice were either fed a KD, a diet with the same macronutrient composition but low in methyl donors (low methyl KD, LMKD), or control diet. After 4, 8 or 12 weeks plasma was collected for the quantification of: (1) nutritional ketosis, (i.e., the ketone body beta-hydroxybutyrate using a colorimetric assay); (2) homocysteine by HPLC; (3) the methylating potential S-adenosylmethionine to S-adenosylhomocysteine ratio (AdoHcy/AdoMet) by LC-MS/MS; and (4) the inflammatory cytokine monocyte chemoattractant protein 1 (MCP1) by ELISA. After 12 weeks, aortas were collected to assess: (1) the vascular AdoHcy/AdoMet ratio; (2) the volume of atherosclerotic lesions by high-field magnetic resonance imaging (14T-MRI); and (3) the content of specific epigenetic tags (H3K27me3 and H3K27ac) by immunofluorescence. The results confirmed the presence of nutritional ketosis in KD and LMKD mice but not in the control mice. As expected, mild HHcy was only detected in the LMKD-fed mice. Significantly decreased MCP1 plasma levels and plaque burden were observed in control mice versus the other two groups, together with an increased content of one of the investigated epigenetic tags (H3K27me3) but not of the other (H3K27ac). Moreover, we are unable to detect any significant differences at the p < 0.05 level for MCP1 plasma levels, vascular AdoMet:AdoHcy ratio levels, plaque burden, and specific epigenetic content between the latter two groups. Nevertheless, the systemic methylating index was significantly decreased in LMKD mice versus the other two groups, reinforcing the possibility that the levels of accumulated homocysteine were insufficient to affect vascular transmethylation reactions. Further studies addressing nutritional ketosis in the presence of mild HHcy should use a higher number of animals and are warranted to confirm these preliminary observations.

Diet-Induced Mild Hyperhomocysteinemia in Mice Fed a Ketogenic Diet Does Not Alter the Development of Atherosclerosis nor Specific Epigenetic Content

Objectives

Elevated plasma homocysteine (Hcy), or hyperhomocysteinemia (HHcy), is a risk factor for atherosclerosis by mechanisms still elusive. A possibility includes the alteration of specific epigenetic tags at lysine 27 of histone H3 (H3K27) due to hypomethylating stress. Similarly, ketogenic diets (KD), or very-low carbohydrate diets, which stimulate ketosis, and may also affect the epigenetic content on the H3K27 residue. Studies connecting the effects of dietary ketosis, mild HHcy, and specific epigenetic dysregulation are lacking. We hypothesize that diet-induced HHcy and ketosis will induce H3K27 hypomethylation combined with increased acetylation to produce a pro-atherogenic phenotype.

Methods

Seven-week-old male apoe−/− (apolipoprotein E-deficient) mice, a model for human atherosclerosis, were fed ad libitum a KD (in %kcal: fat, 81; carbohydrate, 1; protein, 18; n = 4–6) or HHcy-KD (same macronutrients, with added methionine and reduced methyl donors; n = 4). After 4, 8 and 12 wk of diet treatment, plasma was collected to quantify ketosis via beta-hydroxybutyrate levels (OH-But) by a colorimetric assay, and measure Hcy by HPLC. At the endpoint, mice were euthanized and aortas were collected for quantification of the vascular methylation index, S-adenosylmethionine to S-adenosylHcy ratio by LC-MS-MS; 3-D analysis of the atherosclerotic plaque burden by magnetic resonance imaging; and quantification of the epigenetic tags H3K27me3 and H3K27ac using immunohistochemistry.

Results

A sustained ketosis was detected through elevated OH-But levels in both KD and HHcy-KD mice. HHcy was mildly but significantly (P &lt; 0.05) elevated in HHcy-KD-mice compared to KD-mice after 4 wk (19.5 ± 2.3 vs 4.5 ± 0.6 µM) and 12 wk (17.2 ± 2.1 vs 4.4 ± 0.9 µM). Nevertheless, no significant differences were observed in aortic methylation index, plaque accumulation, or content of the H3K27me3 or H3K27ac epigenetic tags between the two groups of mice.

Conclusions

While mild HHcy was achieved in HHcy-KD mice, this phenotype failed to induce vascular hypomethylation, atherosclerosis progression or specific epigenetic dysregulation, suggesting that a more severe Hcy accumulation may be necessary to cause vascular toxicity and specific epigenetic dysregulation.

Funding Sources

Huck Institutes of the Life Sciences

An Atherogenic Diet Disturbs Aquaporin 5 Expression in Liver and Adipocyte Tissues of Apolipoprotein E-Deficient Mice: New Insights into an Old Model of Experimental Atherosclerosis

The dysfunction of vascular endothelial cells is profoundly implicated in the pathogenesis of atherosclerosis and cardiovascular disease, the global leading cause of death. Aquaporins (AQPs) are membrane channels that facilitate water and glycerol transport across cellular membranes recently implicated in the homeostasis of the cardiovascular system. Apolipoprotein-E deficient (apoE-/-) mice are a common model to study the progression of atherosclerosis. Nevertheless, the pattern of expression of AQPs in this atheroprone model is poorly characterized. In this study, apoE-/- mice were fed an atherogenic high-fat (HF) or a control diet. Plasma was collected at multiple time points to assess metabolic disturbances. At the endpoint, the aortic atherosclerotic burden was quantified using high field magnetic resonance imaging. Moreover, the transcriptional levels of several AQP isoforms were evaluated in the liver, white adipocyte tissue (WAT), and brown adipocyte tissue (BAT). The results revealed that HF-fed mice, when compared to controls, presented an exacerbated systemic inflammation and atherosclerotic phenotype, with no major differences in systemic methylation status, circulating amino acids, or plasma total glutathione. Moreover, an overexpression of the isoform AQP5 was detected in all studied tissues from HF-fed mice when compared to controls. These results suggest a novel role for AQP5 on diet-induced atherosclerosis that warrants further investigation.

Altering the Mechanical Load Environment During Growth Does Not Affect Adult Achilles Tendon Properties in an Avian Bipedal Model

Tendon mechanical properties respond to altered load in adults, but how load history during growth affects adult tendon properties remains unclear. To address this question, we adopted an avian model in which we altered the mechanical load environment across the growth span. Animals were divided at 2 weeks of age into three groups: (1) an exercise control group given the opportunity to perform high-acceleration movements (EXE, n = 8); (2) a sedentary group restricted from high-intensity exercise (RES, n = 8); and (3) a sedentary group also restricted from high-intensity exercise and in which the gastrocnemius muscles were partially paralyzed using repeated bouts of botulinum toxin-A injections (RES-BTX, n = 8). Video analysis of bird movement confirmed the restrictions eliminated high-intensity exercise and did not alter time spent walking and sitting between groups. At skeletal maturity (33–35 weeks) animals were sacrificed for analysis, consisting of high-field MRI and material load testing, of both the entire free Achilles tendon and the tendon at the bone-tendon junction. Free tendon stiffness, modulus, and hysteresis were unaffected by variation in load environment. Further, the bone-tendon junction cross-sectional area, stress, and strain were also unaffected by variations in load environment. These results suggest that: (a) a baseline level of low-intensity activity (standing and walking) may be sufficient to maintain tendon growth; and (b) if this lower threshold of tendon load is met, non-mechanical mediated tendon growth may override the load-induced mechanotransduction signal attributed to tendon remodeling in adults of the same species. These results are important for understanding of musculoskeletal function and tendon health in growing individuals.

In vitro real-time magnetic resonance imaging for quantification of thrombosis

OBJECTIVES

Thrombosis is a leading cause of failure for cardiovascular devices. While computational simulations are a powerful tool to predict thrombosis and evaluate the risk for medical devices, limited experimental data are available to validate the simulations. The aim of the current study is to provide experimental data of a growing thrombus for device-induced thrombosis.

MATERIALS AND METHODS

Thrombosis within a backward-facing step (BFS), or sudden expansion was investigated, using bovine and human blood circulated through the BFS model for 30 min, with a constant inflow rate of 0.76 L/min. Real-time three-dimensional flow-compensated magnetic resonance imaging (MRI), supported with Magnevist, a contrast agent improving thrombus delineation, was applied to quantify thrombus deposition and growth within the model.

RESULTS

The study showed that the BFS model induced a flow recirculation region, which facilitated thrombosis. By 30 min, in comparison to bovine blood, human blood resulted in smaller thrombus formation, in terms of the length (13.3 ± 0.6 vs. 18.1 ± 1.3 mm), height (2.3 ± 0.1 vs. 2.6 ± 0.04 mm), surface area exposed to blood (0.67 ± 0.03 vs 1.05 ± 0.08 cm²), and volume (0.069 ± 0.004 vs. 0.093 ± 0.007 cm³), with p < 0.01. Normalization of the thrombus measurements, which excluded the flow recirculation effects, suggested that the thrombus sizes increased during the first 15 min and stabilized after 20 min. Blood properties, including viscosity, hematocrit, and platelet count affected thrombosis.

CONCLUSION

For the first time, contrast agent-supported real-time MRI was performed to investigate thrombus deposition and growth within a sudden expansion. This study provides experimental data for device-induced thrombosis, which is valuable for validation of computational thrombosis simulations.

A Ketogenic Diet Is Protective Against Atherosclerosis in Apolipoprotein E Knockout Mice

Objectives

A ketogenic diet (KD) positively impacts cardiovascular disease (CVD) risk factors yet its effect on atherosclerosis, the main cause of CVD, is elusive. We hypothesize that, when compared to a high-fat diet (HF), KD protects from atherosclerosis.

Methods

Seven-week-old male Apoe−/− mice, a model for human atherosclerosis, were fed ad libitum (%kcal) KD (81-fat, 1-carbohydrate, 18-protein; n = 4) or HF (40-fat, 42-carbohydrate, 18-protein; n = 5). After 4, 8 and 12 weeks, plasma was collected and used to (1) quantify beta-hydroxybutyrate levels (OH-But) by a colorimetric assay; or (2) assess systemic inflammation, a key feature associated with atherosclerosis, using a panel of inflammatory cytokines; or (3) explore diet-driven changes in levels of atherosclerosis-relevant metabolites using a targeted metabolomic approach by triple quadrupole mass spectrometry. At the endpoint, mice were euthanized and their perfusion-fixed aortas were subjected to 3-D analysis by magnetic resonance imaging to quantify the extent of atherosclerosis. Data were reconstructed using Matlab and segmented to obtain atherosclerotic plaque volumes using Avizo 9.0.

Results

The inflammatory cytokines were significantly (P &lt; 0.05, Student's t-test) elevated in HF-mice compared to KD-mice after 12 weeks; MIP-1α, (25 ± 13 vs 13 ± 4 pg/mol), MCP-1 (165 ± 67 vs 69 ± 23 pg/mol), TNF-α(51 ± 17 vs 35 ± 5 pg/mol), and IL-1β (2 ± 2 vs 0.6 ± 0.1 pg/mol). OH-But levels were always significantly higher in KD-mice than in HF-mice, thus confirming the presence of ketosis in KD-mice. Significant changes in the plasma metabolome of KD-mice, when compared to HF-mice, were present for dimethylated arginines, gut-derived metabolites, certain bile acids, some acylcarnitines and ceramides, certain sphingolipids and cholesterol esters, and constituents of the major intracellular antioxidant glutathione. Lastly, aortic plaque burden was significantly decreased in KD mice (2.77 ± 1.02%) than in HF mice (13.94 ± 3.72%).

Conclusions

KD was associated with decreased inflammation, changes in several metabolic intermediates and an atheroprotective effect based on MRI analysis.

Funding Sources

Huck Institutes of the Life Sciences; Graduate Program in Nutritional Sciences.

Mild Hyperhomocysteinemia Induced by a Hypomethylating Diet Does Not Favor Aortic Plaque Formation in apoE Knockout Mice (P24-037-19)

Objectives

Hyperhomocysteinemia is an independent risk factor for atherosclerosis and cardiovascular disease through mechanisms still incompletely defined. We investigated the impact of mild diet-induced accumulation of homocysteine on atherosclerotic plaque formation in apoE knockout (KO) mice, a model for atherosclerosis in humans. We hypothesize that diet induced hyperhomocysteinemia will promote plaque development.

Methods

7 wk-old male apoE-KO mice (n = 5) were fed a methyl-deficient diet for 16 wk. The diet consisted of a purified high (40%)-fat high-methionine diet with restricted levels of B vitamins and choline (HypoMet). A second group of animals (control, n = 5) was fed a normal-methyl matched diet. After 4 and 12 wk, plasma homocysteine was quantified by reverse phase HPLC with fluorometric detection, and a panel of inflammatory cytokines (MCP-1; TNF-; IL-17A/F; IL-2; IL-6, IL-10; KC/GRO; MIP-1; IFN-) were assayed (U-plex, Meso Scale Discovery). After 16 wk, mice were euthanized and perfusion-fixed aortas were stained for lipids (Oil Red-O) and subjected to 2-D-quantification of stained plaque (Image J software), and to 3-D analysis by magnetic resonance imaging (MRI, Agilent 14-tesla microimaging system). Standard 3-D gradient echo imaging yielded a resolution of 20 microns isotropic. Data were reconstructed using Matlab and segmented to obtain plaque volumes using Avizo 9.0.

Results

HypoMet-mice had significantly higher plasma homocysteine (µM), when compared to controls, at 4 wk (10.6 ± 4.5 vs 2.3 ± 0.8, P < 0.05) and 12 wk (7.6 ± 1.5 vs 2.5 ± 1.1, P < 0.05). No significant differences were observed in inflammatory cytokines. Surprisingly, Oil Red-O staining revealed that HypoMet-mice did not display more plaque coverage (37 ± 6.9%) than controls (54.4 ± 10.4%). 14-T MRI results (Fig.1) confirmed that HypoMet-mice did not present higher plaque volumes than controls (0.61 ± 0.18 mm3 vs 1.2 ± 0.35 mm3, for HypoMet mice vs controls).

Conclusions

A mild accumulation of homocysteine, induced by a methyl-deficient diet, did not favor atherosclerosis formation in the aortas of apoE-KO mice. Future analysis of intracellular hypomethylation may explain the observed effects of mild hyperhomocysteinemia on plaque formation.

Funding Sources

Graduate Program and University Funding.

Supporting Tables, Images and/or Graphs

Neurobiological effect of selective brain cooling after concussive injury

The search for effective treatment facilitating recovery from concussive injury, as well as reducing risk for recurrent concussion is an ongoing challenge. This study aimed to determine: a) feasibility of selective brain cooling to facilitate clinical symptoms resolution, and b) biological functions of the brain within athletes in acute phase of sports-related concussion. Selective brain cooling for 30 minutes using WElkins sideline cooling system was administered to student-athletes suffering concussive injury (n=12; tested within 5±3 days) and those without history of concussion (n=12). fMRI and ASL sequences were obtained before and immediately after cooling to better understanding the mechanism by which cooling affects neurovascular coupling. Concussed subjects self-reported temporary relief from physical symptoms after cooling. There were no differences in the number or strength of functional connections within Default Mode Network (DMN) between groups prior to cooling. However, we observed a reduction in the strength and number of connections of the DMN with other ROIs in both groups after cooling. Unexpectedly, we observed a significant increase in cerebral blood flow (CBF) assessed by ASL after selective cooling in the concussed subjects compared to the normal controls. We suggest that compromised neurovascular coupling in acute phase of injury may be temporarily restored by cooling to match CBF with surges in the metabolic demands of the brain. Upon further validation, selective brain cooling could be a potential clinical tool in the minimization of symptoms and pathological changes after concussion.

Porous tissue strands: avascular building blocks for scalable tissue fabrication

The scalability of cell aggregates such as spheroids, strands, and rings has been restricted by diffusion of nutrient and oxygen into their core. In this study, we introduce a novel concept in generating tissue building blocks with micropores, which represents an alternative solution for vascularization. Sodium alginate porogens were mixed with human adipose-derived stem cells, and loaded into tubular alginate capsules, followed by de-crosslinking of the capsules. The resultant cellular structure exhibited a porous morphology and formed cell aggregates in the form of strands, called 'porous tissue strands (pTSs).' Three-dimensional reconstructions show that pTSs were able to maintain ∼25% porosity with a high pore interconnectivity (∼85%) for 3 weeks. Owing to the porous structure, pTSs showed up-regulated cell viability and proliferation rate as compared to solid counterparts throughout the culture period. pTSs also demonstrated self-assembly capability through tissue fusion yielding larger-scale patches. In this paper, chondrogenesis and osteogenesis of pTSs were also demonstrated, where the porous microstructure up-regulated both chondrogenic and osteogenic functionalities indicated by cartilage- and bone-specific immunostaining, quantitative biochemical assessment and gene expression. These findings indicated the functionality of pTSs, which possessed controllable porosity and self-assembly capability, and had great potential to be utilized as tissue building blocks in distinct applications such as cartilage and bone regeneration.

Design of a sustainable prepolarizing magnetic resonance imaging system for infant hydrocephalus

OBJECTIVES

The need for affordable and appropriate medical technologies for developing countries continues to rise as challenges such as inadequate energy supply, limited technical expertise, and poor infrastructure persist. Low-field magnetic resonance imaging (LF MRI) is a technology that can be tailored to meet specific imaging needs within such countries. Its low power requirements and the possibility of operating in minimally shielded or unshielded environments make it especially attractive. Although the technology has been widely demonstrated over several decades, it is yet to be shown that it can be diagnostic and improve patient outcomes in clinical applications. We here demonstrate the robustness of prepolarizing MRI (PMRI) technology for assembly and deployment in developing countries for the specific application to infant hydrocephalus. Hydrocephalus treatment planning and management requires only modest spatial resolution, such that the brain can be distinguished from fluid-tissue contrast detail within the brain parenchyma is not essential.

MATERIALS AND METHODS

We constructed an internally shielded PMRI system based on the Lee-Whiting coil system with a 22-cm diameter of spherical volume.

RESULTS

In an unshielded room, projection phantom images were acquired at 113 kHz with in-plane resolution of 3 mm × 3 mm, by introducing gradient fields of sufficient magnitude to dominate the 5000 ppm inhomogeneity of the readout field.

DISCUSSION

The low cost, straightforward assembly, deployment potential, and maintenance requirements demonstrate the suitability of our PMRI system for developing countries. Further improvement in image spatial resolution and contrast of LF MRI will broaden its potential clinical utility beyond hydrocephalus.

A functional imaging study of germinating oilseed rape seed

Germination, the process whereby a dry, quiescent seed springs to life, has been a focus of plant biologist for many years, yet the early events following water uptake, during which metabolism of the embryo is restarted, remain enigmatic. Here, the nature of the cues required for this restarting in oilseed rape (Brassica napus) seed has been investigated. A holistic in vivo approach was designed to display the link between the entry and allocation of water, metabolic events and structural changes occurring during germination. For this, we combined functional magnetic resonance imaging with Fourier transform infrared microscopy, fluorescence-based respiration mapping, computer-aided seed modeling and biochemical tools. We uncovered an endospermal lipid gap, which channels water to the radicle tip, from whence it is distributed via embryonic vasculature toward cotyledon tissues. The resumption of respiration is initiated first in the endosperm, only later spreading to the embryo. Sugar metabolism and lipid utilization are linked to the spatiotemporal sequence of tissue rehydration. Together, this imaging study provides insights into the spatial aspects of key events in oilseed rape seeds leading to germination. It demonstrates how seed architecture predetermines the pattern of water intake, which sets the stage for the orchestrated restart of life.

Integration of Brain and Skull in Prenatal Mouse Models of Apert and Crouzon Syndromes

The brain and skull represent a complex arrangement of integrated anatomical structures composed of various cell and tissue types that maintain structural and functional association throughout development. Morphological integration, a concept developed in vertebrate morphology and evolutionary biology, describes the coordinated variation of functionally and developmentally related traits of organisms. Syndromic craniosynostosis is characterized by distinctive changes in skull morphology and perceptible, though less well studied, changes in brain structure and morphology. Using mouse models for craniosynostosis conditions, our group has precisely defined how unique craniosynostosis causing mutations in fibroblast growth factor receptors affect brain and skull morphology and dysgenesis involving coordinated tissue-specific effects of these mutations. Here we examine integration of brain and skull in two mouse models for craniosynostosis: one carrying the FGFR2c C342Y mutation associated with Pfeiffer and Crouzon syndromes and a mouse model carrying the FGFR2 S252W mutation, one of two mutations responsible for two-thirds of Apert syndrome cases. Using linear distances estimated from three-dimensional coordinates of landmarks acquired from dual modality imaging of skull (high resolution micro-computed tomography and magnetic resonance microscopy) of mice at embryonic day 17.5, we confirm variation in brain and skull morphology in Fgfr2c^C342Y/+ mice, Fgfr2^+/S252W mice, and their unaffected littermates. Mutation-specific variation in neural and cranial tissue notwithstanding, patterns of integration of brain and skull differed only subtly between mice carrying either the FGFR2c C342Y or the FGFR2 S252W mutation and their unaffected littermates. However, statistically significant and substantial differences in morphological integration of brain and skull were revealed between the two mutant mouse models, each maintained on a different strain. Relative to the effects of disease-associated mutations, our results reveal a stronger influence of the background genome on patterns of brain-skull integration and suggest robust genetic, developmental, and evolutionary relationships between neural and skeletal tissues of the head.

The influence of complex and threatening environments in early life on brain size and behaviour

The ways in which challenging environments during development shape the brain and behaviour are increasingly being addressed. To date, studies typically consider only single variables, but the real world is more complex. Many factors simultaneously affect the brain and behaviour, and whether these work independently or interact remains untested. To address this, zebrafish (Danio rerio) were reared in a two-by-two design in housing that varied in structural complexity and/or exposure to a stressor. Fish experiencing both complexity (enrichment objects changed over time) and mild stress (daily net chasing) exhibited enhanced learning and were less anxious when tested as juveniles (between 77 and 90 days). Adults tested (aged 1 year) were also less anxious even though fish were kept in standard housing after three months of age (i.e. no chasing or enrichment). Volumetric measures of the brain using magnetic resonance imaging (MRI) showed that complexity alone generated fish with a larger brain, but this increase in size was not seen in fish that experienced both complexity and chasing, or chasing alone. The results highlight the importance of looking at multiple variables simultaneously, and reveal differential effects of complexity and stressful experiences during development of the brain and behaviour.

Design of a mobile, homogeneous, and efficient electromagnet with a large field of view for neonatal low-field MRI

OBJECTIVE

In this work, a prototype of an effective electromagnet with a field-of-view (FoV) of 140 mm for neonatal head imaging is presented. The efficient implementation succeeded by exploiting the use of steel plates as a housing system. We achieved a compromise between large sample volumes, high homogeneity, high B0 field, low power consumption, light weight, simple fabrication, and conserved mobility without the necessity of a dedicated water cooling system.

MATERIALS AND METHODS

The entire magnetic resonance imaging (MRI) system (electromagnet, gradient system, transmit/receive coil, control system) is introduced and its unique features discussed. Furthermore, simulations using a numerical optimization algorithm for magnet and gradient system are presented.

RESULTS

Functionality and quality of this low-field scanner operating at 23 mT (generated with 500 W) is illustrated using spin-echo imaging (in-plane resolution 1.6 mm × 1.6 mm, slice thickness 5 mm, and signal-to-noise ratio (SNR) of 23 with a acquisition time of 29 min). B0 field-mapping measurements are presented to characterize the homogeneity of the magnet, and the B0 field limitations of 80 mT of the system are fully discussed.

CONCLUSION

The cryogen-free system presented here demonstrates that this electromagnet with a ferromagnetic housing can be optimized for MRI with an enhanced and homogeneous magnetic field. It offers an alternative to prepolarized MRI designs in both readout field strength and power use. There are multiple indications for the clinical medical application of such low-field devices.

Reconstruction and morphometric analysis of the nasal airway of the white-tailed deer (Odocoileus virginianus) and implications regarding respiratory and olfactory airflow

Compared with other mammals (e.g., primates, rodents, and carnivores), the form and function of the ungulate nasal fossa, in particular the ethmoidal region, has been largely unexplored. Hence, the nasal anatomy of the largest prey species remains far less understood than that of their predators, rendering comparisons and evolutionary context unclear. Of the previous studies of nasal anatomy, none have investigated the detailed anatomy and functional morphology of the white-tailed deer (Odocoileus virginianus), a species that is ubiquitous throughout North and Central America and in northern regions of South America. Here, nasal form and function is quantitatively investigated in an adult white-tailed deer using high-resolution magnetic resonance imaging, combined with anatomical reconstruction and morphometric analysis techniques. The cross-sectional anatomy of the airway is shown and a three-dimensional anatomical model of the convoluted nasal fossa is reconstructed from the image data. A detailed morphometric analysis is presented that includes quantitative distributions of airway size and shape (e.g., airway perimeter, cross-sectional area, surface area) and the functional implications of these data regarding respiratory and olfactory airflow are investigated. The white-tailed deer is shown to possess a long, double scroll maxilloturbinal that occupies approximately half of the length of the nasal fossa and provides a large surface area for respiratory heat and moisture exchange. The ethmoidal region contains a convoluted arrangement of folded ethmoturbinals that appear to be morphologically distinct from the single and double scroll ethmoturbinals found in most other non-primates. This complex folding provides a large surface area in the limited space available for chemical sensing, due to the expansive maxilloturbinal. Morphologically, the white-tailed deer is shown to possess a dorsal meatus that leads to an olfactory recess, a nasal architecture that has been shown in other non-primate species to cause unique nasal airflow patterns to develop during sniffing that are optimized for odorant delivery to the sensory part of the nose. Additionally, we demonstrate that, during respiration, airflow in the nasal vestibule and the anterior maxilloturbinal region may be transitional or turbulent, in which case turbulent mixing is expected to enhance respiratory heat and moisture exchange, which could be an important contribution to thermoregulation and water conservation in the white-tailed deer.

In vitro quantification of time dependent thrombus size using magnetic resonance imaging and computational simulations of thrombus surface shear stresses

Thrombosis and thromboembolization remain large obstacles in the design of cardiovascular devices. In this study, the temporal behavior of thrombus size within a backward-facing step (BFS) model is investigated, as this geometry can mimic the flow separation which has been found to contribute to thrombosis in cardiac devices. Magnetic resonance imaging (MRI) is used to quantify thrombus size and collect topographic data of thrombi formed by circulating bovine blood through a BFS model for times ranging between 10 and 90 min at a constant upstream Reynolds number of 490. Thrombus height, length, exposed surface area, and volume are measured, and asymptotic behavior is observed for each as the blood circulation time is increased. Velocity patterns near, and wall shear stress (WSS) distributions on, the exposed thrombus surfaces are calculated using computational fluid dynamics (CFD). Both the mean and maximum WSS on the exposed thrombus surfaces are much more dependent on thrombus topography than thrombus size, and the best predictors for asymptotic thrombus length and volume are the reattachment length and volume of reversed flow, respectively, from the region of separated flow downstream of the BFS.

Effects of subconcussive head trauma on the default mode network of the brain

Although they are less severe than a full blown concussive episodes, subconcussive impacts happen much more frequently and current research has suggested this form of head trauma may have an accumulative effect and lead to neurological impairment later in life. To investigate the acute effects that subconcussive head trauma may have on the default mode network of the brain resting-state, functional magnetic resonance was performed. Twenty-four current collegiate rugby players were recruited and all subjects underwent initial scanning 24 h prior to a scheduled full contact game to provide a baseline. Follow-up scanning of the rugby players occurred within 24 h following that game to assess acute effects from subconcussive head trauma. Differences between pre-game and post-game scans showed both increased connectivity from the left supramarginal gyrus to bilateral orbitofrontal cortex and decreased connectivity from the retrosplenial cortex and dorsal posterior cingulate cortex. To assess whether or not a history of previous concussion may lead to a differential response following subconcussive impacts, subjects were further divided into two subgroups based upon history of previous concussion. Individuals with a prior history of concussion exhibited only decreased functional connectivity following exposure to subconcussive head trauma, while those with no history showed increased connectivity. Even acute exposure to subconcussive head trauma demonstrates the ability to alter functional connectivity and there is possible evidence of a differential response in the brain for those with and without a history of concussion.

Quantifying the effects of inactin vs Isoflurane anesthesia on gastrointestinal motility in rats using dynamic magnetic resonance imaging and spatio-temporal maps

BACKGROUND

Anesthetics are commonly applied in animal studies of gastrointestinal (GI) function. Different anesthetics alter smooth-muscle motility in different ways. The aim of this study is to quantify and compare non-invasively with magnetic resonance imaging (MRI) the motility patterns of the rat gut when anesthetized with inactin vs isoflurane anesthetics in the fed state.

METHODS

Rats were given an oral gavage of MRI contrast agent for improved visualization of the GI tract. Two-dimensional images through the jejunum of the pre- and postanesthetized rat in the fed state were acquired every 168 ms. Image registration, segmentation, and postprocessing algorithms were applied to produce spatio-temporal maps that were used to quantify peristaltic and segmental motions in the jejunum region interspersed between periods of inactivity.

KEY RESULTS

There were significantly longer periods of inactivity in the rats treated with isoflurane than in those treated with inactin (179.9 ± 22.4 s vs 17.7 ± 10.3 s). The speed of propagation and wavelength of peristalsis, and the frequency and speed of pattern switching of segmental motility, were higher (p < 0.05) in rats treated with inactin.

CONCLUSIONS & INFERENCES

Isoflurane and inactin anesthetics produce significantly different motility behavior with the rat's GI tract in the fed state. Isoflurane anesthetic, results in a reduced frequency of occurrence of motility periods and an overall reduced level of motility in comparison with inactin.

Preconception zinc deficiency disrupts postimplantation fetal and placental development in mice

Zinc is an essential nutrient for optimal fertility, but the effects of preconception zinc deficiency on postimplantation development are not known. Female mice were fed a control or a zinc-deficient diet (ZDD) for 4-5 days before ovulation (preconception). Embryonic and/or placental development were evaluated on Days 3.5, 6.5, 10.5, 12.5, and 16.5 of pregnancy. The findings show a decrease in embryo length (31%, Day 10.5; 13%, Day 12.5; 10%, Day 16.5) and weight (23%, Day 16.5) in embryos from mothers fed a ZDD preconception. Zinc deficiency also caused a high incidence of pregnancy loss (46%, Day 10.5; 34%, Day 12.5; 51%, Day 16.5) compared to control (2%, Day 10.5; 7%, Day 12.5; 9%, Day 16.5). ZDD embryos transferred to normal recipients were 38% smaller and implantation rate was only 10% compared to 40% for controls. Trophoblast cell differentiation and implantation on Day 6.5 of pregnancy were compromised by preconception zinc deficiency. On Day 12.5 of pregnancy, placenta weight and area of fetal placenta were decreased 37% and 31%, respectively, by preconception zinc deficiency. Consistent with a smaller fetal placenta, expression of key placental transcripts, including Ar, Esx1, Syna, Tfeb, Dlx3, and Gcm1 mRNA, but not Ctsq mRNA, were decreased 30%-70% in the ZDD group. Preconception zinc deficiency caused 41%-57% of embryos to exhibit delayed or aberrant neural tube development, as examined by light microscopy and magnetic resonance imaging. Collectively, the findings provide evidence for the importance of preconception zinc in promoting optimal fertility and oocyte developmental potential.

Seed architecture shapes embryo metabolism in oilseed rape

Constrained to develop within the seed, the plant embryo must adapt its shape and size to fit the space available. Here, we demonstrate how this adjustment shapes metabolism of photosynthetic embryo. Noninvasive NMR-based imaging of the developing oilseed rape (Brassica napus) seed illustrates that, following embryo bending, gradients in lipid concentration became established. These were correlated with the local photosynthetic electron transport rate and the accumulation of storage products. Experimentally induced changes in embryo morphology and/or light supply altered these gradients and were accompanied by alterations in both proteome and metabolome. Tissue-specific metabolic models predicted that the outer cotyledon and hypocotyl/radicle generate the bulk of plastidic reductant/ATP via photosynthesis, while the inner cotyledon, being enclosed by the outer cotyledon, is forced to grow essentially heterotrophically. Under field-relevant high-light conditions, major contribution of the ribulose-1,5-bisphosphate carboxylase/oxygenase-bypass to seed storage metabolism is predicted for the outer cotyledon and the hypocotyl/radicle only. Differences between in vitro- versus in planta-grown embryos suggest that metabolic heterogeneity of embryo is not observable by in vitro approaches. We conclude that in vivo metabolic fluxes are locally regulated and connected to seed architecture, driving the embryo toward an efficient use of available light and space.

A noninvasive platform for imaging and quantifying oil storage in submillimeter tobacco seed

While often thought of as a smoking drug, tobacco (Nicotiana spp.) is now considered as a plant of choice for molecular farming and biofuel production. Here, we describe a noninvasive means of deriving both the distribution of lipid and the microtopology of the submillimeter tobacco seed, founded on nuclear magnetic resonance (NMR) technology. Our platform enables counting of seeds inside the intact tobacco capsule to measure seed sizes, to model the seed interior in three dimensions, to quantify the lipid content, and to visualize lipid gradients. Hundreds of seeds can be simultaneously imaged at an isotropic resolution of 25 µm, sufficient to assess each individual seed. The relative contributions of the embryo and the endosperm to both seed size and total lipid content could be assessed. The extension of the platform to a range of wild and cultivated Nicotiana species demonstrated certain evolutionary trends in both seed topology and pattern of lipid storage. The NMR analysis of transgenic tobacco plants with seed-specific ectopic expression of the plastidial phosphoenolpyruvate/phosphate translocator, displayed a trade off between seed size and oil concentration. The NMR-based assay of seed lipid content and topology has a number of potential applications, in particular providing a means to test and optimize transgenic strategies aimed at the manipulation of seed size, seed number, and lipid content in tobacco and other species with submillimeter seeds.

The use of magnetic resonance spectroscopy in the subacute evaluation of athletes recovering from single and multiple mild traumatic brain injury

Advanced neuroimaging techniques have shown promise in highlighting the subtle changes and nuances in mild traumatic brain injury (MTBI) even though clinical assessment has shown a return to pre-injury levels. Here we use ¹H-magnetic resonance spectroscopy (¹H-MRS) to evaluate the brain metabolites N-acetyl aspartate (NAA), choline (Cho), and creatine (Cr) in the corpus callosum in MTBI. Specifically, we looked at the NAA/Cho, NAA/Cr, and Cho/Cr ratios in the genu and splenium. We recruited 20 normal volunteers (NV) and 28 student athletes recovering from the subacute phase of MTBI. The MTBI group was categorized based upon the number of MTBIs and time from injury to ¹H-MRS evaluation. Significant reductions in NAA/Cho and NAA/Cr ratios were seen in the genu of the corpus callosum, but not in the splenium, for MTBI subjects, regardless of the number of MTBIs. MTBI subjects recovering from their first MTBI showed the greatest alteration in NAA/Cho and NAA/Cr ratios. Time since injury to ¹H-MRS acquisition was based upon symptom resolution and did not turn out to be a significant factor. We observed that as the number of MTBIs increased, so did the length of time for symptom resolution. Unexpected findings from this study are that MTBI subjects showed a trend of increasing NAA/Cho and NAA/Cr ratios that coincided with increasing number of MTBIs.

The arrangement of fascicles in whole muscle

The architecture of the muscle fascicles, here meaning their lengths and their arrangement relative to one another, has important implications for the force a muscle can produce. Therefore, quantifying this architectural arrangement and understanding the implications of the architecture are important for understanding muscle function in vivo. There were two purposes of this study: (1) to assess, via blunt dissection, the number and the length of all the fascicles comprising the First Dorsal Interosseous (FDI) muscle and (2) to visually identify, via magnetic resonance imaging (MRI), the arrangement of the fascicles comprising the FDI. Simple blunt dissection of all the fascicles comprising four FDI muscles and their subsequent measurement demonstrated that the fascicles comprising the whole muscle were not as long as the muscle belly from which they were extracted. Muscle fascicles are surrounded by connective tissue hence the paths of the fascicles in two whole FDI muscles were identified via MRI by tracking the connective tissue surrounding the fascicles. The fascicles had a spiral pattern along the length of each muscle, within both muscles many of the fascicles were arranged in series with other fascicles. These architectural features of the fascicles of the FDI have important implications for the force-length and force-velocity properties of the whole muscle.

Surveying the plant's world by magnetic resonance imaging

Understanding the way in which plants develop, grow and interact with their environment requires tools capable of a high degree of both spatial and temporal resolution. Magnetic resonance imaging (MRI), a technique which is able to visualize internal structures and metabolites, has the great virtue that it is non-invasive and therefore has the potential to monitor physiological processes occurring in vivo. The major aim of this review is to attract plant biologists to MRI by explaining its advantages and wide range of possible applications for solving outstanding issues in plant science. We discuss the challenges and opportunities of MRI in the study of plant physiology and development, plant-environment interactions, biodiversity, gene functions and metabolism. Overall, it is our view that the potential benefit of harnessing MRI for plant research purposes is hard to overrate.

Fractional Order Analysis of Sephadex Gel Structures: NMR Measurements Reflecting Anomalous Diffusion

We report the appearance of anomalous water diffusion in hydrophilic Sephadex gels observed using pulse field gradient (PFG) nuclear magnetic resonance (NMR). The NMR diffusion data was collected using a Varian 14.1 Tesla imaging system with a home-built RF saddle coil. A fractional order analysis of the data was used to characterize heterogeneity in the gels for the dynamics of water diffusion in this restricted environment. Several recent studies of anomalous diffusion have used the stretched exponential function to model the decay of the NMR signal, i.e., exp[-(bD)(α)], where D is the apparent diffusion constant, b is determined the experimental conditions (gradient pulse separation, durations and strength), and α is a measure of structural complexity. In this work, we consider a different case where the spatial Laplacian in the Bloch-Torrey equation is generalized to a fractional order model of diffusivity via a complexity parameter, β, a space constant, μ, and a diffusion coefficient, D. This treatment reverts to the classical result for the integer order case. The fractional order decay model was fit to the diffusion-weighted signal attenuation for a range of b-values (0 < b < 4,000 s-mm(-2)). Throughout this range of b values, the parameters β, μ and D, were found to correlate with the porosity and tortuosity of the gel structure.

Metabolic alterations in corpus callosum may compromise brain functional connectivity in MTBI patients: an 1H-MRS study

After clinical resolution of signs and symptoms of mild traumatic brain injury (MTBI) it is still not clear if there are residual abnormalities of structural or functional brain networks. We have previously documented disrupted interhemispheric functional connectivity in 'asymptomatic' concussed individuals during the sub-acute phase of injury. Testing of 15 normal volunteers (NV) and 15 subacute MTBI subjects was performed within 24h of clinical symptoms resolution and medical clearance for the first stage of aerobic activity. In this MRS study we report: (a) both in the genu and splenium of the corpus callosum NAA/Cho and NAA/Cr ratios were significantly (p<0.05) lower in MTBI subjects shortly after the injury compared to NVs, and (b) the metabolic ratio NAA/Cho in the splenium significantly correlated with the magnitude of inter-hippocampal functional connectivity in normal volunteers, but not in MTBI. This novel finding supports our hypothesis that the functional disruption of interhemispheric brain networks in MTBI subjects results from compromised metabolic integrity of the corpus callosum and that this persists despite apparent clinical return to baseline.

Low and High Field Magnetic Resonance for in Vivo Analysis of Seeds

Low field NMR has been successfully used for the evaluation of seed composition and quality, but largely only in crop species. We show here that 1.5T NMR provides a reliable means for analysing the seed lipid fraction present in a wide range of species, where both the seed size and lipid concentration differed by >10 fold. Little use of high field NMR has been made in seed research to date, even though it potentially offers many opportunities for studying seed development, metabolism and storage. Here we demonstrate how 17.5T and 20T NMR can be applied to image seed structure, and analyse lipid and metabolite distribution. We suggest that further technical developments in NMR/MRI will facilitate significant advances in our understanding of seed biology.

The dynamics of brain and cerebrospinal fluid growth in normal versus hydrocephalic mice

OBJECT

Hydrocephalus has traditionally been quantified by linear measures of ventricular size, with adjunct use of cortical mantle thickness. However, clinical outcome depends on cognitive function, which is more directly related to brain volume than these previous measures. The authors sought to quantify the dynamics of brain and ventricular volume growth in normal compared with hydrocephalic mice.

METHODS

Hydrocephalus was induced in 14-day-old C57BL/6 mice by percutaneous injection of kaolin into the cisterna magna. Nine hydrocephalic and 6 normal mice were serially imaged from age 2-12 weeks with a 14.1-T MR imaging unit. Total brain and ventricle volumes were calculated, and linear discriminant analysis was applied.

RESULTS

Two very different patterns of response were seen in hydrocephalic mice compared with mice with normative growth. In one pattern (3 mice) brain growth was normal despite accumulation of CSF, and in the second pattern (6 mice) abnormal brain enlargement was accompanied by increased CSF volume along with parenchymal edema. In this latter pattern, spontaneous ventricular rupture led to normalization of brain volume, implying edema from transmantle pressure gradients. These 2 patterns of hydrocephalus were significantly discriminable using linear discriminant analysis (p < 0.01). In contrast, clinically relevant measurements of head circumference or frontal and occipital horn ratios were unable to discriminate between these patterns.

CONCLUSIONS

This study is, to the authors' knowledge, the first serial quantification of the growth of brain and ventricle volumes in normal versus hydrocephalic development. The authors' findings demonstrate the feasibility of constructing normative curves of brain and fluid growth as complements to normative head circumference curves. By measuring brain volumes, distinct patterns of brain growth and enlargement can be observed, which are more likely linked to cognitive development and clinical outcome than fluid volumes alone.

A multiscale lattice Boltzmann model of macro- to micro-scale transport, with applications to gut function

Nutrient absorption in the small intestine cannot occur until molecules are presented to the epithelial cells that line intestinal villi, finger-like protrusions under enteric control. Using a two-dimensional multiscale lattice Boltzmann model of a lid-driven cavity flow with 'villi' at the lower surface, we analyse the hypothesis that muscle-induced oscillatory motions of the villi generate a controlled 'micro-mixing layer' (MML) that couples with the macro-scale flow to enhance absorption. Nutrient molecules are modelled as passive scalar concentrations at high Schmidt number. Molecular concentration supplied at the cavity lid is advected to the lower surface by a lid-driven macro-scale eddy. We find that micro-scale eddying motions enhance the macro-scale advective flux by creating an MML that couples with the macro-scale flow to increase absorption rate. We show that the MML is modulated by its interactions with the outer flow through a diffusion-dominated layer that separates advection-dominated macro-scale and micro-scale mixed layers. The structure and strength of the MML is sensitive to villus length and oscillation frequency. Our model suggests that the classical explanation for the existence of villi--increased absorptive surface area--is probably incorrect. The model provides support for the potential importance of villus motility in the absorptive function of the small intestine.

Reliability and validity of a novel muscle contusion device

CONTEXT

Many models have been employed to replicate skeletal muscle injury associated with trauma; however, most are restricted to 1 level of severity.

OBJECTIVE

To create and validate an injury-producing device that could generate multiple levels of injury severity.

DESIGN

Validation study.

PATIENTS OR OTHER PARTICIPANTS

Twenty-six male Wistar rats, 3 to 4 months old.

INTERVENTION(S)

A contusion device was developed and its ability to deliver consistent impacts was validated alone and in the presence of an experimental animal. A free-falling mass (267 g) was adjusted to the desired height (40, 50, 60, or 70 cm) and then dropped.

MAIN OUTCOME MEASURE(S)

Peak load, peak displacement, impulse, energy, and velocity peak were measured. Injury severity was determined using magnetic resonance imaging.

RESULTS

Outcome measures observed from the device alone were different by height (F(18,136) = 21.807, P < .001, 1-beta = 1.0). Outcomes using the experimental animals were also dependent on height (F(14,102) = 68.679, P < .001, 1-beta = 1.0). Linear regression analyses indicated that height accounted for 17% to 89% of the variance.

CONCLUSIONS

Mild to moderate and moderate to severe injuries can be replicated with this device, which will be useful in evaluating clinical treatments on acute muscle injury.

Experimental and numerical assessment of MRI-induced temperature change and SAR distributions in phantoms and in vivo

It is important to accurately characterize the heating of tissues due to the radiofrequency energy applied during MRI. This has led to an increase in the use of numerical methods to predict specific energy absorption rate distributions for safety assurance in MRI. To ensure these methods are accurate for actual MRI coils, however, it is necessary to compare to experimental results. Here, we report results of some recent efforts to experimentally map temperature change and specific energy absorption rate in a phantom and in vivo where the only source of heat is the radiofrequency fields produced by the imaging coil. Results in a phantom match numerical simulation well, and preliminary results in vivo show measurable temperature increase. With further development, similar methods may be useful for verifying numerical methods for predicting specific energy absorption rate distributions and in some cases for directly measuring temperature changes and specific energy absorption rate induced by the radiofrequency fields in MRI experiments.

Brain phenotypes in two FGFR2 mouse models for Apert syndrome

Apert syndrome (AS) is one of at least nine disorders considered members of the fibroblast growth factor receptor (FGFR) -1, -2, and -3-related craniosynostosis syndromes. Nearly 100% of individuals diagnosed with AS carry one of two neighboring mutations on Fgfr2. The cranial phenotype associated with these two mutations includes coronal suture synostosis, either unilateral (unicoronal synostosis) or bilateral (bicoronal synostosis). Brain dysmorphology associated with AS is thought to be secondary to cranial vault or base alterations, but the variation in brain phenotypes within Apert syndrome is unexplained. Here, we present novel three-dimensional data on brain phenotypes of inbred mice at postnatal day 0 each carrying one of the two Fgfr2 mutations associated with AS. Our data suggest that the brain is primarily affected, rather than secondarily responding to skull dysmorphogenesis. Our hypothesis is that the skull and brain are both primarily affected in craniosynostosis and that shared phenogenetic developmental processes affect both tissues in craniosynostosis of Apert syndrome.

Faraday shields within a solenoidal coil to reduce sample heating: numerical comparison of designs and experimental verification

A comparison of methods to decrease RF power dissipation and related heating in conductive samples using passive conductors surrounding a sample in a solenoid coil is presented. Full-Maxwell finite difference time domain numerical calculations were performed to evaluate the effect of the passive conductors by calculating conservative and magnetically-induced electric field and magnetic field distributions. To validate the simulation method, experimental measurements of temperature increase were conducted using a solenoidal coil (diameter 3 mm), a saline sample (10 mM NaCl) and passive copper shielding wires (50 microm diameter). The temperature increase was 58% lower with the copper wires present for several different input powers to the coil. This was in good agreement with simulation for the same geometry, which indicated 57% lower power dissipated in the sample with conductors present. Simulations indicate that some designs should be capable of reducing temperature increase by more than 85%.

Radiofrequency coils for magnetic resonance microscopy

Given the several orders of magnitude fewer spins per voxel for MR microscopy than for conventional MRI, efficient coil design is important to obtain sufficient signal-to-noise within reasonable data acquisition times. As MR microscopy is typically performed using very high magnetic fields, coil design must also incorporate the effects of increased component losses and skin-depth-dependent resistance, as well as radiation losses and phase effects for coils when conductor dimensions constitute a substantial fraction of the electromagnetic wavelength. For samples much less than 1 mm in size, wire solenoids or microfabricated planar coils are used. For samples with diameters of several millimeters, saddle, birdcage, Alderman-Grant or millipede coils become the preferred choice. Recent advances in multiple-coil probes and phased arrays have been used to reduce data acquisition time and/or increase sample throughput, and small superconducting coils have shown significant improvements in signal-to-noise over equivalently sized room-temperature coils.

High Q calcium titanate cylindrical dielectric resonators for magnetic resonance microimaging

At high magnetic fields radiation losses, wavelength effects, self-resonance, and the high resistance of typical components all contribute to increased losses in conventional RF coil designs. High permittivity ceramic dielectric resonators create strong uniform magnetic fields in a compact structure at high frequencies and can potentially solve some of the challenges of high field coil design. In this study an NMR probe was constructed for operation at 600 MHz (14.1T) using an inductively fed CaTiO(3) (relative permittivity of 156) cylindrical hollow bore dielectric resonator. The design has an unmatched Q value greater than 2000, and the electric field is largely confined to the dielectric itself, with near zero values in the hollow bore which accommodates the sample. Experimental and simulation mapping of the RF field show good agreement, with the ceramic resonator giving a pulse width approximately 25% less than a loop gap resonator of similar inner dimensions. High resolution images, with voxel dimensions less than 50 microm(3), have been acquired from fixed zebrafish samples, showing excellent delineation of several fine structures.

Quantitative analysis of peristaltic and segmental motion in vivo in the rat small intestine using dynamic MRI

Conventional methods of quantifying segmental and peristaltic motion in animal models are highly invasive; involving, for example, the external isolation of segments of the gastrointestinal (GI) tract either from dead or anesthetized animals. The present study was undertaken to determine the utility of MRI to quantitatively analyze these motions in the jejunum region of anesthetized rats (N = 6) noninvasively. Dynamic images of the GI tract after oral gavage with a Gd contrast agent were acquired at a rate of six frames per second, followed by image segmentation based on a combination of three-dimensional live wire (3D LW) and directional dynamic gradient vector flow snakes (DDGVFS). Quantitative analysis of the variation in diameter at a fixed constricting location showed clear indications of both segmental and peristaltic motions. Quantitative analysis of the frequency response gave results in good agreement with those acquired in previous studies using invasive measurement techniques. Principal component analysis (PCA) of the segmented data using active shape models resulted in three major modes. The individual modes revealed unique spatial patterns for peristaltic and segmental motility.

Temperature mapping near the surface of ultrasound transducers using susceptibility- compensated magnetic resonance imaging

Magnetic resonance imaging (MRI)-based temperature mapping very close to the surface of an ultrasound transducer is not possible due to the large magnetic susceptibility- induced image artifacts that arise from the materials used in transducer construction. Here, it is shown in phantoms that "susceptibility-compensated" MRI sequences can be used to measure thermal increases approximately 1 mm from the surface of a 4-element cymbal array transducer, which has been used widely for noninvasive transdermal drug delivery. The estimated temperatures agree well with those measured using thermocouples.

Feasibility and safety of longitudinal magnetic resonance imaging in a rodent model with intracortical microwire implants

The purpose of this communication is to investigate (1) the feasibility of carrying out longitudinal magnetic resonance imaging (MRI) studies in animals with implanted microwire electrodes adapted for MRI compatibility, (2) the effect of MRI studies on the quality of neurophysiological recordings, (3) the use of MRI to study the extent and recovery of tissue damage due to electrode insertion and (4) histological tissue damage due to MRI. There was no evidence of chronic neural damage caused by repeated MRI by any of the measures used nor any statistical difference in the quality of the electrophysiological recordings between animals that had undergone MRI scans and those that had not.

Magnetic resonance imaging of acute injury in rats and the effects of buprenorphine on limb volume

The purposes of this study were to determine 1) whether magnetic resonance imaging (MRI)-based T2 mapping and measurements of limb volume can differentiate injured and uninjured tissue after blunt trauma to rat hindlimbs and 2) whether administration of buprenorphine influences these assessments. Male Wistar rats (age, 3 to 4 mo) underwent blunt contusion injury to the posterior aspect of the hindlimb; MRI was conducted at 6, 12, 24, 48, 72, and 96 h after injury. The imaging results showed that administration of buprenorphine had no effect on the T2 value {area under the receiver operating characteristic [ROC] curve: with drug, 0.869 [95% confidence interval (CI), 0.78 to 0.96]; without drug, 0.809 [95% CI, 0.72 to 0.90]} but did influence limb volume [area under the ROC curve; without drug, 0.954 (95% CI, 0.92 to 0.99); with drug, 0.713 (95% CI, 0.61 to 0.82)]. When using MRI to determine the extent of injury or to track injury over time, calculated limb volumes may lose sensitivity to detect injury, due to the intrinsic increase in volume from morphine-derived drugs. During administration of morphine derivatives, T2 maps may provide more accurate assessments of muscle tissue injury both initially after injury and over time.

Quantitative imaging of oil storage in developing crop seeds

In this article, we present a tool which allows the rapid and non-invasive detection and quantitative visualization of lipid in living seeds at a variety of stages using frequency-selected magnetic resonance imaging. The method provides quantitative lipid maps with a resolution close to the cellular level (in-plane 31 microm x 31 microm). The reliability of the method was demonstrated using two contrasting subjects: the barley grain (monocot, 2% oil, highly compartmentalized) and the soybean grain (dicot, 20% oil, economically important oilseed). Steep gradients in local oil storage were defined at the organ- and tissue-specific scales. These gradients were closely coordinated with tissue differentiation and seed maturation, as revealed by electron microscopy and biochemical and gene expression analysis. The method can be used to elucidate similar oil accumulation processes in different tissues/organs, as well as to follow the fate of storage lipids during deposition and subsequent mobilization.